Hello @scixing ,
Welcome to Microsoft Q&A forum.
Is it your custom control? I don’t think you need to export it.
Generally, you can create a custom control and add it into VS Toolbox by right-clicking the white space of Toolbox > Choose Items… > Browse… If you want to use it on another machine, you can move your custom control to another machine and add it into the Toolbox again.
Best Regards,
Tianyu
If the answer is the right solution, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.