How would you go about making a custom idlemarker. Adding to the WallLeaning/Sitting/pushups/etc. For example I want to make one of the dance animations from groovatron into an idle marker. Is this possible?

You can certainly make new idle markers. Just go to Miscellaneous --> Idle Markers in the object window and right click in the list and select new. Enter a unique ID and start adding idles. Whether the Groovatron supplies idles to use or not, I have no idea. Also, idles themselves have conditions associated with them, so just because you add them to an idle marker does not mean that they will play in every situation.

I didn't know about misc > idle markers. Whats the difference between that and the ones (floorsitmarker/wallmarker/etc) world objects > furniture?

Furniture have idles associated with them to take advantage of the furniture - like a sit animation for chairs, sleep anim for beds, wall lean for walls, and sit on the floor for floors. But Idle markers can play a series of idles or random idles from a list of them and can be placed. They can also be used in patrols and cause dialogue to be spoken. They are useful for setting up scenes.

Okay forget everything I said earlier, I've run into another problem.

I've taken one of the Umpa dance animations and added it as a special idle under LOOSE and added it to a new idle marker
The problem is the actor will loop the animation forever
I have tried nifskoping but have only got animation errors and animation CTD's.

I just want the actor to do one or two loops of the animation and then go back to sandbox mode

Look where you added it under loose, it should have spaces where you can type Min loop times, or max. I'm guessing you left those blank. Put 2 in each and every time they should only loop twice.

For some reason those boxes are blacked out.

I think it has something to do with the .kf file because
I tried changing the name value in nifskope, which removes the blacked out boxes and lets me put values for loop amount.. but this causes animation to make the game to crash.
Chang cycle type doesn't yield anything either

So I assume this is in a specific location since you have the marker and everything and you won't be worrying about doing this at random times. Although you could do that to, but anyway, you could make a different package for the dancing that you set up that happens in the middle of sandboxing.

Yeah I guess that's the way to go, either by package or scripting..Its just a little more work than just putting an idle marker.

I think the way Umpa designed the animation is that it is missing an end value for the loop. Wouldn't want to go any further than that unless I had documentation for blender animating for fallout 3.

Umpa does not use Blender he uses Max... I field questions about animations from him from time to time all have related to Max, Oblivion or FO3.

As far as the animation goes I would have to see it to know what your doing wrong.

The only way for the dance animation to stop is to replay the animation (the animation's script will stop it) or to use a "reset.kf". This makes them unusable as idle markers (unless you added triggers on top of the idlemarkers) and it also blacks out the loop quantity boxes in the GECK's "idle animations"

Having them available as idle markers is just a minor convenience because scripting can work around this.

Again, I would modify the animations myself but I know so little about animating in blender and there doesn't seem to be any fallout 3 animation tutorials.