One other item that gets to be an issue is the local history of a workspace.
Designer getting slower and slower?
Can't find your disk space anymore?
Poke your nose in the Designer workspace(es) and see if you, like me, have an outrageously full history directory.
The path you should examine is relative to the workspace location. So, if your workspace is c:\Users\Weaver\workspace, for an arbitrary example right off the top of my head, the history that I'm referring to will be:
Substitute the path to your workspace above.
This folder contains a set of folders named with two hexadecimal digits, such as 1f, 23, etc.
The purpose of this area is to store file revision changes from your project to act as a failsafe backup. It's a core eclipse function, not a Designer one.
The problem is manifold:
Eclipse doesn't always clean it up properly, so files accumulate over time and don't go away. Ever.
Cleanup is only done on proper Eclipse exit. Crashes don't count. Force close also doesn't count. Also, see 1.
IDM projects use a metric ton of files, seriously, a huge freaking amount of them. Many of them change all the time. Loads of tiny files, some big ones, all of them changing all of the time for seemingly simple changes to the project. This causes the history to fill up rapidly.
Basically, you should clear out this folder from time to time. Mine had around a gigabyte of storage in it spread across over 150k files. It took an hour to delete. This made a huge difference in performance and stopped a hang that I was getting in Designer.
There is a setting that you can change in Designer prefs to reduce the impact of this history and, perhaps, reduce it's terrible growth.
From Designer, Window menu -> Preferences. Expand "General -> Workspace -> Local History". Change the values to smaller values. I went with 1 in all cases.