Since MOS3JOKER said 'polyline', I'm guessing the he/she had a custom linetype in an earlier file rather than an object?
MOS3JOKER - if it is a linetype, simply go to Options > Attributes > Attribute Manager, switch to the linetype tab. On the right, open your prior 14 file and find the custom linetype you need. Select it and then if on the left the index number shown is not in use, select Overwrite; otherwise select Append. OK out to save the linetype in the current file.
One of the forum moderators AC 27 USA and earlier • macOS Ventura 13.6.2, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB
Erika wrote: Actually, I had checked the 14 and 15 INT library parts, and it is a parking library part in 14, but not 15.
Exactly!... by the way, thanks everybody for your replies! I haven't been able to reply to you guys earlier. I sort of worked my way around so I could add the polyline object from archicad 14 to archicad 15 without having to add the whole library. In case anyone is interested, this is how I did it. Opened a new file in archicad 14, placed the object, then saved as ".pla" so that only the object would be saved and not the whole library. Then opened it and extracted the object so I could take just the object and macros folders (the others are not necesary and will give you error reports of duplicate parts). Put those 2 folders inside another folder, named it after the object and that's it.
Thanks a lot guys! Sort of new to these forums so I hope this wasn't asked before
EDIT: I haven't tried it yet but it seems Erika's method is WAY simpler than mine. I'll try it later. Thanks!