This is a port of the STBL management tool I did for TS3, with an added function to batch copy strings from one STBL to another in the same package. This is kind of a quickie and needs more testing, especially to make sure the modified STBLs work in-game, so use caution and keep a backup of your original package.
Extract and run EasySTBLmanager.exe.
Edit: There's a weird bug when using the Musher function which I'll get to ASAP. Use at your own risk meanwhile.
And another edit: The bug was in my brain, I confused Spanish with Portuguese. That'll teach me to test when I'm tired. Everything seems to be working okay, but keep backups.
6/20/17: Version 18.104.22.168 - Cosmetic changes to correct problems with display and resizing.
6/20/17: Version 22.214.171.124 - Fixed errors causing modified STBLs to crash the game and garbled display of strings in the tool after modification.
Please do not PM me with mod, tutorial, or general modding questions or problems; post them in the thread for the mod or tutorial or post them in the appropriate forum.
Visit my blogs for other Sims content: Online Sims - general mods for Sims 3 Offline Sims - adult mods for Sims 3 and Sims 4