diff --git a/ui (gen4)/features/collections.js b/ui (gen4)/features/collections.js
index 628b713b..74cd7607 100755
--- a/ui (gen4)/features/collections.js	
+++ b/ui (gen4)/features/collections.js	
@@ -2034,17 +2034,20 @@ module.CollectionTags = core.ImageGridFeatures.Feature({
 			function(_, gids, title){
 				var that = this
 				var local_tag_names = this.config['collection-local-tags'] || []
+				gids = gids || this.current
+				gids = gids instanceof Array ? gids : [gids]
 
 				// prevent global tag removal...
-				var tags = this.data.tags
-				delete this.data.tags
+				var tags = this.data.tags.__index
+				// XXX do we need this??? (leftover from prev tak implementation)
+				//delete this.data.tags
 
 				return function(){
 					// update local tags...
 					local_tag_names.forEach(function(tag){
-						tags[tag] = that.data.makeSparseImages(tags[tag], true) })
+						tags[tag] = tags[tag].subtract(gids) })
 
-					this.data.tags = tags
+					//this.data.tags.__index = tags
 				}
 			}],
 		// save .local_tags to json...
diff --git a/ui (gen4)/features/filesystem.js b/ui (gen4)/features/filesystem.js
index f6881634..f485e13f 100755
--- a/ui (gen4)/features/filesystem.js	
+++ b/ui (gen4)/features/filesystem.js	
@@ -396,6 +396,8 @@ var FileSystemLoaderActions = actions.Actions({
 					that.loadOrRecover(index) 
 						.then(function(){
 							force_full_save
+								// XXX remove as soon as merged index save is done...
+								&& loaded.length == 1
 								&& that.markChanged('all')
 						})
 				})
diff --git a/ui (gen4)/imagegrid/data.js b/ui (gen4)/imagegrid/data.js
index bb7de218..9cf1239e 100755
--- a/ui (gen4)/imagegrid/data.js	
+++ b/ui (gen4)/imagegrid/data.js	
@@ -3557,7 +3557,7 @@ var DataWithTags2Prototype = {
 	// XXX test...
 	split: function(){
 		var res = DataWithTags2Prototype.__proto__.split.apply(this, arguments)
-		res.tags = res.tags.filter(res.order)
+		res.tags = res.tags.keep(res.order)
 		return res
 	},
 	clone: function(){
diff --git a/ui (gen4)/imagegrid/formats.js b/ui (gen4)/imagegrid/formats.js
index ed9e7e4d..ccf5d1db 100755
--- a/ui (gen4)/imagegrid/formats.js	
+++ b/ui (gen4)/imagegrid/formats.js	
@@ -42,7 +42,6 @@ function(data){
 module.VERSIONS['2.0'] =
 function(data, cmp){
 	//data = data.version < '2.0' ? module.VERSIONS['2.0'](data) : data
-	console.log('Updating data to: ', '2.0')
 
 	var res = {
 		data: {
@@ -103,8 +102,6 @@ function(data){
 
 	var res = {}
 	res.version = '3.0'
-	console.log('Updating data to: ', res.version)
-
 	res.current = data.current
 	res.order = data.order.slice()
 	res.ribbon_order = data.ribbon_order == null ? [] : data.ribbon_order.slice()
@@ -137,7 +134,6 @@ function(data){
 	var res = data.version < '3.0' ? module.VERSIONS['3.0'](data) : data
 
 	res.version = '3.1'
-	console.log('Updating data to: ', res.version)
 
 	data.tags
 		&& (res.tags = { tags: data.tags })
diff --git a/ui (gen4)/imagegrid/tags.js b/ui (gen4)/imagegrid/tags.js
index 38377fc2..7230d354 100755
--- a/ui (gen4)/imagegrid/tags.js	
+++ b/ui (gen4)/imagegrid/tags.js	
@@ -633,6 +633,60 @@ var TagsPrototype = {
 							: null) }) },
 	
 
+	// Tag set/list API...
+	//
+	// XXX should this be join or add???
+	join: function(...others){
+		var that = this
+		var index = this.__index || {}
+		others
+			.forEach(function(other){
+				Object.entries(other.__index || {})
+					.forEach(function(e){
+						index[e[0]] = new Set([...(index[e[0]] || []), ...e[1]]) }) })
+		Object.keys(index).length > 0 
+			&& this.__index == null
+			&& (this.__index = index)
+		return this
+	},
+	// Keep only the given values...
+	//
+	// 	.keep(value, ..)
+	// 	.keep([value, ..])
+	// 		-> this
+	//
+	keep: function(...values){
+		values = (values.length == 1 && values[0] instanceof Array) ? 
+			values.pop() 
+			: values
+		var res = this.clone()
+
+		Object.entries(res.__index || {})
+			.forEach(function(e){
+				res.__index[e[0]] = e[1].intersect(values) })
+
+		return res
+	},
+	// Remove the given values...
+	//
+	// 	.remove(value, ..)
+	// 	.remove([value, ..])
+	// 		-> this
+	//
+	remove: function(...values){
+		values = (values.length == 1 && values[0] instanceof Array) ? 
+			values.pop() 
+			: values
+		var res = this.clone()
+
+		Object.entries(res.__index || {})
+			.forEach(function(e){
+				res.__index[e[0]] = e[1].subtract(values) })
+
+		return res
+	},
+
+
 	// Query API...
 	//
 	// The language (JS):
@@ -752,30 +806,6 @@ var TagsPrototype = {
 	},
 
 
-	join: function(...others){
-		var that = this
-		var index = this.__index || {}
-		others
-			.forEach(function(other){
-				Object.entries(other.__index || {})
-					.forEach(function(e){
-						index[e[0]] = new Set([...(index[e[0]] || []), ...e[1]]) }) })
-		Object.keys(index).length > 0 
-			&& this.__index == null
-			&& (this.__index = index)
-		return this
-	},
-	// XXX create a new tagset with only the given values...
-	// XXX this should support a function...
-	filter: function(values){
-		var res = this.clone()
-		Object.values(res.__index || {})
-			.forEach(function(s){
-				values.forEach(function(v){ s.delete(v) }) })
-		return res
-	},
-
-
 	// Object utility API...
 	//
 	// 	.clone()