You may be ready to add beneficiaries (especially after copying an executor to the beneficiaries side), but unable to edit/add new until you enter the allocation settings (pictured below).
In some cases (e.g. you are only applying for probate, and do not need to set each person's residual entitlement; or the listed beneficiaries are only entitled to specific/cash bequests), you may want to skip this section.
You can simply click "Save" to move ahead.
If you are not entering each person's entitlement, you can simply leave their share value at 0%.
If the listed beneficiaries are only entitled to specific/cash bequests, you can then click on the three-dot menu next to their names to edit their profile, and change their entitlement type from Residual to Legacy.