I'm pretty sure that small sling is a carry strap, like on a suitcase. Probably for the tripod, or perhaps for several ammo cans?
I assume the slings are hungarian, from looking at your photos it seems they used different materials for them.
Here are some pics of the pkm accs I have, Both sets came with the Hungarian pkm sets ordered from MGS when they first came in, The green set didnt come with the sling but has the other accs and green can handle that matches. The tan set appears complete and matches the handle on the cans.
I was told the spider looking strap assembly was for banding the ground mount bag and gun bag together for transport so they dont get seperated. Dont know for sure.
Also included a few pics of the book that was in a plastic bag tied arounf the muzzle of one of the bbls, first entry shows 1978, followed by a 1980, then 1982, last entry is 2000
pics are big so click the links, will be happy to scan the entire book that came with the gun if someone can translate.
No problem, if you find slings I sure could use another.
On the straps in this pic ,
the big one is the sling for the rifle, the spider like harness seems to tie the ground mount bag and gun bag together and the two smaller padded straps are the shoulder straps to pack the entire rig on your back, the short little strap with clips ties the left and right straps together across your chest so they dont spread.