In GSE addon when making a rotation for Feral Cat Druid the ability/spell Mangle can not be specified to Cat Form.
When you are in Cat Form it want to use Mangle Bear Form and also when in Bear Form when you want to use Swipe it wants to use Cat Form Swipe.

When you setup a rotation and try to specify Mangle(Cat Form) the "(Cat Form)" part disappears and just revert back to Mangle, same with Swipe.

To reproduce it you just need to make a simple rotation with Mangle and Swipe and try to specify the ability/spell for Cat Form or Bear Form.

Screenshots trying to show whats going on in game.

Typed in the Mangle(cat form)

After you typed it in, it disappears and reverts back to Mangle

Showing in Bottom Right corner of picture that Mangle in the rotation requires Bear Form.

Expected behavior should be the ability/spell Mangle and Swipe to not remove the (Cat Form) or (Bear Form) after the ability/spell.

GSE.lua File.
GSE.lua.txt

Using Windows 10 64bit
Game Version Classic Cataclysm in Pre Patch version 4.4.0.54525

GSE version - GSE-3.1.68
Downloaded it from curseforge client app pulling from https://www.curseforge.com

Additional context:
In the GSE.lua file the Mangle spell id is 33878 and changing it from ["Mangle"] = 33878, to ["Mangle"] = "Mangle(cat form)", works in game until you teleport, hearth or go into a dungeon then it reverts back to ["Mangle"] = 33878, and require you to be in Bear Form again.
Also when you go to Options in GSE, Troubleshooting and Edit Spell Cache under the enUS tab you can see Spell Name Mangle and it's Spell ID 33878, when you change the Spell ID 33878 to Mangle(cat form) the rotation then work but when you teleport, hearth or go in a dungeon it stays Mangle(cat form) but the rotation states you need to be in Bear Form then.

Fixing this will break Retail. The issue is a WoW issue. When GSE asks for the spell id for "Swipe (Cat Form)" WoW returns the same ID as for Bear form. The only way to fix this without breaking the rest of the translator for Retail as they both use the same code base is to simply not translate that spell.

The workaround is
/use Swipe (Cat Form)

Note: If sharing a template with another player in another language they will need to translate this manually into their own language.

Found another workaround where the whole rotation does work with your Chosen Form but in a Wow Macro form and can be combined with GSE macro, link to page https://wowlazymacros.com/t/wow-classic-cataclysm-druid-swipe-in-macro/40618/20