Maybe this helps you a little?

I open the trimmer with the clip, select the time I want the clip to run, then hit the blue button with arrow, this sends the edited clip back to the timeline at cursor position. But when I check in properties at the length of the clip it still shows the original length, not the trimmed length. So if you want to stabilise the footage, it will do that, but for the full length of the original clip not the edited 10 second one! Hope that makes sense?

The property you see is the property of the source clip, not the property of the timeline event.

Yes, that's why I'm saying there doesn't seem a need for a trimmer, you can simply drag the clip to desired length! Although i'm sure the trimmer was put on the program for a purpose, but can't work out what for! Even if you add no FX such as stabilise for example, the clips edited length is still the same as original length!

Use the setting shown in the Hamburger Menu to show the event length of your trimmed event.

Adding the Stabilize FX should be done as Event FX and AFTER the trimming is done.

I've just done some images, to show what I mean.

The source clip length doesn't matter for editing. It's the events's clip length what matters and that's what the trimmer trims. All non-linear editing systems work this way.

Properties always shows the original clips length. Trimming the clip does not affect the original clip. It only adjusts pointers. It is non-destructive.

OK, but if i have a original 10 second clip and apply stabilise, its done in no time at all, if I trim a clip to 10 seconds it takes much longer... So i'm really confused that if you have two 10 second clips surely the time to stabilise should be roughly the same and not 1 minute for one clip and 3 minutes for the other!

As 3Point said above: You need to apply the Stabilize FX as Event FX, not as Media FX. Applied as Event FX it will affect the trimmed portion only.

I'm going to try that now, anyway thanks guys, it was baffling me.... And I may return again lol

@John-Marshall

The properties that you are looking at are of the original video clip, which remains untouched. NLE's are non-destructive editors. It doesn't matter what you do on the timeline to that video clip, the original file remains intact. Vegas only uses that video file and remembers its name, where it is on your computer, which part to use - from xx frames to xx frames, and any effects that you put on it all within the project file. It does not keep a copy within the project file; it always needs access to the original file. It does not actually cut and replace the original file. If it did, we would all be in big trouble.