It would be helpful for others if you would add the type of system you are using to your profile.
Then others will have a clue to your system as the problem.
Im not saying it is. Just that it is VERY helpful to know as some problems can be with the type of system set up.
Once your part is saved, do you think this part makes your computer longer to render a view than when it is not a part of the rendering? Try to render the project as both hidden line and as picture with the object and without. This way you can tell if the part and its complexity is just going to take longer.
I have not had any problems saving out GDL objects, as in taking 30 minutes to do a save. Though I have not done much complex Library part creation yet in AC 8.1v1.
Others who read this site will help in this regard, but will need to know the version you are using and the system you are using.
Terrence Sturm, Architect
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MBP OSX 10.15.4 Quad Core Intel i7 2.2hz
AC 17 build 5019
AC 22 build 7000
AC 23 build
AC 24 build 5000