changing the column width for a double layered x axis column chart or condense the chart altogether

Hi xangetsu21 
There is no option to reduce the columns' width.
To reduce the size of the x-axis you can consider to :
1. Reduce the space between categories 

2. To change a graph type to dots instead of bars:

This is of course not enough, so you can also resize a canvas width:

Pbix with examples is attached

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Hi xangetsu21 
Yes, + user can manipulate it for his comfort:

actual size is like on desktop

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Yes, view options are personal for the user...
available for all roles, this functionality does not count as an edit.

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Hi xangetsu21 
This slider belongs to the slicer, not to the graph..

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