Atomic Systems

I've been working with RE a little recently, and one thing I've tried is to add siding markers to Stranraer goods yard on Vern's original MSTS Ayr-Stranraer (We have an old PC, and I find this route works very nicely). However 'Interactive Objects' do not appear in the 'Object Selector' dialog box in RE, and I was wondering if someone could tell me a) In which kind of folder in the original MSTS routes are 'Interactive Objects' kept, and b} Should it be fairly easy to copy over?
I'm building my own very basic route anyway in which they are already available, but I'm a little intrigued now as to their location! (And in case anybody takes offence, save from adding a signal box at Ayr I haven't changed any of Vern's hardwork).

Siding markers and platform markers are normally located in the object selector under the category mainline stations, and appear under the unsurprising names of Siding and Platform. If they are not in mainline stations they will be in there somewhere under another category.

Select siding and then place the cursor between the tracks where you want it and left click. The marker should appear. You can then select either end yellow triangle and move it along the track to increase its length. With a yellow triangle selected- right click and a box will appear in which you can name the siding.

Thanks for that, they duly were under 'mainline stations', as opposed to where I'd read they'd be.
Thanks for taking the time to reply,

Clay.