Goto user setting and enable 'Multi Branch' option. For giving multi branch access to the users.

Select Manager for the branch manager, who can create branches and assign branches to the users.

Click on the branches menu.

Form view of the branches. Fillup the details.

Open the user from user setting. Assign the branches and select one default branch.

After that, the default branch will become visible. Click on the default branch, and a dropdown menu will appear in this you will see the all allowed branches.

In the tree view of the analytic accounts, you have the option to group by analytic accounts based on their branches.
Note: This feature allows you to categorize analytic accounts according to their respective branches.

Analytic Accounts Form View. In this section, you will find the selected branch here.

Branch field in the budgetary positions tree view.

Branch field in the budgetary positions form view.

Goto the accounting section and open the configuration menu and click on the budget. Branch field in the budget tree view. Click on a budget to view its details.

Branch field in the budget form view.

Branch field in the analytic items tree view.

If you want to see the budget analysis reports then open the budget analysis from the configuration menu of the account. Branch field in the analytic items tree view.

Branch field in the budget analysis form view.