Rectangular multi mask copy/paste

[FawFuLJJ2]

Idea should work only when in the tileset pane 'masks' is active.

Request similar to 'copy+paste' rectangular function tiles to complete this feature for complete tile importing/exporting.

[FawFuLJJ2]

Bumping this request again:

1. Since december 2022 I've talked with numerous levelmakers that would really like this feature for flexibility and convenience. The steps of rebuilding a tileset: Extracting a full image, looking carefully what height the masks need to be placed in, then saving the new file and rebuild simply takes a lot longer than direct copying. It becomes more complicated the larger the scope of the level.
2. The tile-by-tile mask paste already exists within MLLE (however for some reason doesn't clipboard to PSP or to other instances of MLLE), it would be preferable if that worked too.
3. The features "Tileset > Add new..." and "Set... Build" don't go well together currently. Which is a seperate issue. The text below there is a detailed example and explanation as of why:

Let's say someone is making a castle level, they added two extra castle tilesets to your main castle tileset to start out. It's near the maximum tileset capacity because it also has a lot of backgrounds and animations, you think you need most of it. In time they managed build a large castle, but after finishing they start to feel like something is missing. They come up with the idea of making an outdoor area. They search up grassy tilesets, but they can't find anything that would fit well right away, so they decide to draw some new tiles and some connectors of your own. The result is a 200 tile-sheet that they want to import in their level.

They might not have realised it yet, but they're forced to start from scratch or at the very least partially rebuild the level. Here's an
rundown of all the possible options they tried first:
A. It's already established that copying and pasting masks from the sheet into MLLE is not possible, also not per-tile from and external program like PSP or another instance of MLLE.
B. It's decided to try to extract the full tileset image/mask, cut off the additional tilesets and resize the main tileset to +200 tiles for their new tiles. However upon loading it in it does not work because the tilesets 1+2+3+animated tiles together seem to be near the maximum tileset capacity. Similarily, this would be the same when adding in a 4th tileset.
C. It's decided to try to extract the tileset image, but trying to fit in the 200 tiles in the main tileset. However this also does not work out. Tileset 1 is used for the majority of tiles used in the level, with only 5 tiles left to spare.
D. It's decided to try to to replace tileset 2. Tileset 2 seems to have plenty of unused tiles, however the select tiles that are used are used plentiful throughout. This also does not work, because rebuilding/swapping added tilesets seems not possible. The editor asks to delete the added tileset first before adding a new one, and this removes any chance of rebinding the tileIDs in the level.

In another use case there might be a global masking error, like accidentally moving a sheet a pixel too low. In that case the tileset capacity doesn't even matter, you're basically screwed to completely redo everything.

In my 2023 level I had such an use case of adding in tileset sheet of 160 tiles halfway through, but having to do it again because I noticed a couple of days later that I've moved the whole sheet one pixel too low. Luckily, for this level I didn't use the add tileset feature otherwise I would have had to manually edit 160 tiles 160 times. If there was a paste option, none of this would be an issue. But right now I refrain from ever using the tileset add feature for this reason. The sheet is below as an example.