How to use Front-end builder with multiple store view ( website )
Now you complete a homepage on store view A, when you edit then click "Confirm" on the homepage, the content of the homepage will be saved to cms page, you can find it in the admin
1) Case 1: you have another store view B and you want to use the same cms page on store view B, you only need to go to admin MGS -> General Settings, select store view A then EXPORT the homepage then go to admin MGS -> Theme Setting, select store view B then IMPORT the homepage you just EXPORTED. So store view B will use the same cms page, so you only need to enable builder on the store view A, edit , add or anything then click "Confirm" then the homepage on store view B also will change because they used the same CMS page
2) Case 2: if store view B, you want different something with store view A, you also use IMPORT and EXPORT but before IMPORT to store view B, you must create another cms page first and assign it to store view B in STORES -> Configuration -> Web [GENERAL] then go to admin MGS -> Theme Setting, select store view B then IMPORT the homepage you just EXPORTED. In this case because you created another cms page for store view B, so you can enable the builder on store view B then edit it and your changes will only affect to store view B.
I think that my instruction will help you