I use multiple pages... So on the uppermost, on the right side you'll see 3 lines tap that.. There you'll see bookmark... Tap that and then you'll see successfully added... And then you'll see that chapter in your bookmark..
in mobile version
click on 3 line
then bookmark it
you only bookmark it (chapter) while reading it
I mean first you need to open any chapter
I think this should be help you a lot
https://www.mangago.zone/read-manga/mangago_how_to_guide/
Thanks
How do you guys bookmark a manhwa?