Ok, so you need to find the area file in nwn user folder/modules/temp0. The name of the area file will match its resref - that you can find out in toolset when you open area properties. Also, close all areas in this tileset in toolset if you have them open. And make a backup of your module too just in case.
After that you need to open the area file with *.are extension it with GFF Editor. Either run GFF editor first and open the file from it, or try open the file and when windows ask what to open it with, select browse and find gff editor. GFF editor should be in NWN install folder, but that depends on the distribution Beamdog/GOG/Steam/Diamond, so just search for it beforehand. Alternatively you can download it from vault and put wherever you want: Modified GFF Editor | The Neverwinter Vault
After opening the *.are file you will see something like this:
You need to click in the left side to Tileset and then edit the value in right window to tbs20 (and it should be bog01 originally). Save and exit, then open the area in toolset. If it crashes, then unfortunately the two tilesets aren’t compatile and you have to trash this and close toolset without saving.
But if it doesn’t crash the tilesets are exchangeable (at least in old->newer direction) and you can use this version instead (which doesn’t have the issues that Pstemarie fixed, or at least I haven’t notice them, and which looks much better too). You can also remove the old TB Swamp tileset haks from hak list. Just be sure to change all areas like this, otherwise they crash toolset if you remove the original hak.