Add L(left) and R(right) cycle locator buttons to the transport panel.
When one of these buttons is clicked the selected locator will be set to the current position of the playhead.
Clicking the L button will set the left locator, clicking the R button will set the right locator.
If the current playhead position is to the right of right locator disable the L button.
If the current playhead position is to the left of the left locator disable the R button.
The skip forward and backward buttons will allow setting the locators to the beginning or end of the project.
iPad Pro: 12.9-inch 3rd generation Software version 13.3
Apple Pencil: model A2051