The tab button is really important! This new keyboard moved it and it is not as accessible as before!
Tab will back soon ;)
For now, please take a look at this tutorial – http://support.termius.com/knowledgebase/articles/1135696--getting-started-using-the-extended-keyboard
It will show how you can customize the keyboard as you wish right now!
Current Functionality: Double tap the screen = tab (pretty cool)
At least make some sort of option, so we can make the Tab button appear where it was before...