You can achieve this by using CALL SCREEN ... STARTING AT ... , then using the SUPPRESS DIALOG in PBO processing to bypass the screen processor (dynpro). Then, in PAI processing, use LEAVE TO LIST-PROCESSING followed by the WRITE statements. You can follow this in the function module TMS_UI_POPUP_LEGENDE , which shows the pop-up that you mentioned as a link. The procedure is documented in the online help .
In the ABAP dialog application, you either work with screens or with (interactive) lists . To get a popup, you need to create and CALL custom screen (dynpro). Inside this screen, you transfer control to the list processor. This is the component responsible for the fact that you have ever done WRITE and placed it somewhere on the screen. For some - probably mostly historical - reasons, the team for this is LEAVE TO LIST-PROCESSING . I believe that at some point the supposed flow between the screens and the lists was different from what it became today, and this served as the basis for naming the command this way. From a modern point of view, and especially in your use case, the LEAVE aspect does not make any sense, so just take it as it is and use it.
Also note that this is LEAVE TO LIST PROCESSING - LEAVE LIST-PROCESSING without TO is the opposite operator!