I believe what @hpulsford suggested — copy the folder tree and paste it to another project — will work at first.
But later you will find a big problem when you update the source Object Repository. You have to do copy & paste it to other projects repeatedly. This exercise tends to break. You will make mistakes.
I suppose you have 2 or more Katalon projects which want to share a Object Repository. This implies that those projects are targeting a single URL (a Web Application). Possibly 2 or more people of your team wants to work for the Web app. They have created their own projects, but they realized that most of Test Objects in the Object Repository duplicate. So you are now wondering how to “Reuse page object repository”. Am I right?
I would rather recommend you to consider merging the projects into one, rather than doing copy&pasting the OR across multiple projects. The simpler, the better.
Please find that Test Cases, Test Suites, Test Objects — all of these resources can be structured in a tree of sub-folders. You can name your sub-folders as you like. Your team members would be able to design a folder tree where they can cooperate well without collisions.
Also you should consider putting the project into Git remote repository so that your team members (2 people,3, …, 10, or more) can share a single set of sources. See Shared object repository where I explained how Git enables your team to share a project safely.