This is actually something that irks me somewhat. The Collar was frequently used in the past, for instance when the King wore other countries' Orders at gala events (or even just formal events like the welcoming ceremonies at the beginning of a State Visit). Fair enough, it was before the Order of Merit was founded. But I still think it would look really impressive if the Collar of the Order of St Olav would be worn together with say the Sash of the Order of the Elephant AND the Neck-tie of the Order of Merit (if needs must be).

I just think it is a bit "silly" to gift somebody the Collar knowing that they will never "be allowed" (able) to wear it. Actually, when Harald presented King Willem-Alexander with the Collar and the latter asked when it was worn King Harald jokingly said "I don't know" (me paraphrasing) "I only wear it at the Opening of the Parliament".

https://www.youtube.com/watch?app=desktop&v=llD0xOYOCEI