You are right, the way multi-editing is implemented currently is not very useful - to much hassle to place the cursor at multiple locations and you could easily miss one location.
But with the new Scintilla commands SCI_MULTIPLESELECTADDNEXT and SCI_MULTIPLESELECTADDEACH we got the missing features to enjoy the power of multi-editing. If you are sure you want to overtype all occurences of a certain string send SCI_MULTIPLESELECTADDEACH. If you know that the string only occurs in a few locations near by the cursor (e.g. an if..else...endif block) send SCI_MULTIPLESELECTADDNEXT multiple times. Of course a scripting plugin is needed to be able to send these commands to Scintilla.
In this comment @dail posted some Lua code to emulate SCI_MULTIPLESELECTADDNEXT in Notepad++ versions prior to v7.7 (which introduced the Scintilla version necessary for the two commands mentioned above). I was able to modify it to create an emulator for SCI_MULTIPLESELECTADDEACH as well (maybe I found that code somewhere, too), here are the two functions:
npp.AddShortcut("Selection Add Next", "", function() -- From SciTEBase.cxx local flags = SCFIND_WHOLEWORD -- can use 0 editor:SetTargetRange(0, editor.TextLength) editor.SearchFlags = flags -- From Editor.cxx if editor.SelectionEmpty or not editor.MultipleSelection then local startWord = editor:WordStartPosition(editor.CurrentPos, true) local endWord = editor:WordEndPosition(startWord, true) editor:SetSelection(startWord, endWord) else local i = editor.MainSelection local s = editor:textrange(editor.SelectionNStart[i], editor.SelectionNEnd[i]) local searchRanges = {{editor.SelectionNEnd[i], editor.TargetEnd}, {editor.TargetStart, editor.SelectionNStart[i]}} for _, range in pairs(searchRanges) do editor:SetTargetRange(range[1], range[2]) if editor:SearchInTarget(s) ~= -1 then editor:AddSelection(editor.TargetStart, editor.TargetEnd) -- To scroll main selection in sight editor:ScrollRange(editor.TargetStart, editor.TargetEnd) break end end end -- To turn on Notepad++ multi select markers editor:LineScroll(0, 1) editor:LineScroll(0, -1) end) npp.AddShortcut("Selection Add All", "", function() local flags = SCFIND_WHOLEWORD -- can use 0 local startWord = -1 local endWord = -1 local s = "" editor.SearchFlags = flags if editor.SelectionEmpty or not editor.MultipleSelection then startWord = editor:WordStartPosition(editor.CurrentPos, true) endWord = editor:WordEndPosition(startWord, true) editor:SetSelection(startWord, endWord) else local i = editor.MainSelection startWord = editor.SelectionNStart[i] endWord = editor.SelectionNEnd[i] end s = editor:textrange(startWord, endWord) while true do editor:SetTargetRange(0, editor.TextLength) local i = editor.MainSelection local searchRanges = {{editor.SelectionNEnd[i], editor.TargetEnd}, {editor.TargetStart, editor.SelectionNStart[i]}} local itemFound = false for _, range in pairs(searchRanges) do editor:SetTargetRange(range[1], range[2]) if editor:SearchInTarget(s) ~= -1 then editor:AddSelection(editor.TargetStart, editor.TargetEnd) itemFound = true break end end if editor.TargetStart == startWord and editor.TargetEnd == endWord or not itemFound then break end end -- To turn on Notepad++ multi select markers editor:LineScroll(0, 1) editor:LineScroll(0, -1) end)