My 2009 edition of Trackmaps shows sidings at all the loops except Rogart; all are out of use except Helmsdale and Forsinard. There are sidings at Thurso and Wick, with the latter out of use. There are sidings just north of Invergordon, at Fearn and Altnabreac, with the two latter marked out of use.
There is considerable work going on at Lairg, but it is unclear if this will see the sidings returning to use. However, I can’t find anything on the Friends of the Far North Line site and the Highland Railway Society is also wondering.
That sounds like a good start, sidings at the north of Invergordon included the Aluminium works on the down side and the Distillery on the up side. I pretty sure at one time there was a Harbour branch too, I think from the station area, a flat crossing of the then A9 which went through the town (happy to be corrected but that rings a bell).
An extract from the 1987 Quaill is attached - interestingly that edition makes no mention of Copyright although a more recent one minus some of this detail does!
Glenmorangie Distillery also had a siding, 1.25 miles north of Tain, I recall it in use in the 1960s, on the down side, a single siding with loading bank. It closed in 1970 and was subsequently removed and Google Earth suggests the site is now under a roadway and the bonded warehousing which are now much more extensive than back then.
I think there is a 1960s video (cine) on You Tube which may be helpful
