It's all in ui.h/cpp
Variable uid contains the display settings and there
uint16_t menuPos[UI_MENU_MAXLEVEL]; // Positions in menuhas the menu positions currently active for all menu levels. You need to find the enter command to set it. case UI_ACTION_SD_PRINT: if(sd.sdactive) { pushMenu(&ui_menu_sd_fileselector, false); }
break;is what starts the menu for printing. Problem is that sd files is very special since we can not stor ethe file list in ram (not enough) so it is continously reread from sd card. But maybe just setting pos to 1 afterwards already works.