How to Transfer YouTube Subscriptions from One Account to Another
Tips and Limitations
SubShift: Transfer your YouTube subscriptions - Chrome Web Store How to Transfer YouTube Subscriptions from One Account
Step 5: Customize your archive. Scroll to the bottom of the page. You can leave the defaults: export the CSV
Instead of transferring everything, export the CSV, open it in Excel, and sort by channel name. Remove the dead channels, the ones that haven't uploaded in a year, and the topics you no longer like. Then import the cleaned-up list (usually 20-30 channels) manually without any extensions. open it in Excel
Transfer to New Account: Switch to your new YouTube account in the same browser.