Currently an heatmap tile can contain one variable (field 'value' in view toolbar).
Would it be possible to set multiple fields in one tile. Just for giving users more information per tile.
Whilst you can't actually display multiple measures in each tile, you can get close - for interactive use i.e. where a user is happy to move their mouse over a tile (or across many tiles) you can use Tooltips - go to the Settings > This Tab > Tooltips section and choose the fileds you want to display... you will then see these in a neatly arrange tooltip when you hover over a tile.
If Visokio provided a CHAR() function (generate a text literal from its ASCII/Unicode index) then it would be easy to create a new formula field which concatenated several fields with a newline - CHAR(13) - in between... how about it Visokio?