The (rather excellent) SWTOR UI editor only allows you to increase the scale of elements to 1.25 times the global scale’d size. You can increase it more than that simply by doing a bit of text editing.
First, make sure you save your interface. You also probably want to log out to character select (not sure if it’s required, but may as well).
Next, find where SWTOR saved your interfaces at. Cairenn over at Swtorui posted a full guide on their forums but the short of it is:
C:\Users\USERNAME\AppData\Local\SWTOR\swtor\settings\GUIProfiles (on 7)
C:\Documents and Settings\USERNAME\Local Settings\Application Data\SWTOR\swtor\settings\GUIProfile (on XP)
If you can’t find it, the guide walks you through how to turn on hidden items and such.
Okay, scary stuff over, open up the file with the name of the interface you want in the text editor of your choice. You could also make a new copy of it and save it as a different file name if you’re scared of breaking stuff. Not altogether a bad idea.
If you’re using Notepad for this (instead of say, Notepad++) it’s going to look like a mess, but don’t worry. We’re only looking to change one variable per item, and it’s XML so it’s really easy to find it with searches (Ctrl+F in Notepad). All of the entries have the same names as they do in the editor, so remember that a “hotbar” is a “quickbar” in this game. A few other notables:
Player and Target Frames: PlayerPortrait / TargetPortrait
Target of Target Frame: TargetOfTarget
Operations Frames: RaidFrames (weird, I know)
Once you’ve found your section (did I mention this would be a lot easier if you were using a proper text editor), look for the following <scale tag>, probably looking something like
<scale Type=”3″ Value=”0.900000″ />
Change that Value=”.9″ to whatever number you want. Save, and check it out in-game.
SWTOR saves interfaces at \AppData\Local\SWTOR\swtor\settings\GUIProfiles\EXAMPLE.xml
Open it up, find the <scale> element for the UI item you want to change and change the Value. Sky’s the limit.