How does ThemaMap understand that 2 data columns define a lat/lon point?

Column names must start with a prefix of respectively "longitude" or "latitude" of at least 3 characters long. In case of multiple lat/lon pairs, the prefix must be followed by an underscore ('_') and the same name. The resulting name of the geometry point is a concatenation of the 2 column names separated with a slash ('/')

Examples:

• lat et lon
• latit et longi
• lati et longi
• lat_start et lon_start
• lat_A et lon_A

How to insure that different views of an animation may be compared?

You must not use the maximum size of the objects, but fix the value per pixel quantity.

How make a value to be interpreted as a number and not a text string, or as text and not as number ?

This is principally useful for joins. For sorting or discrete classifications, you may always precise the type of the values.

You can use the add data column adaptor. You can use as expression, for a number: old_column + 0 or old_column * 1
and for text: concat(old_column, "")

Legend elements are not anymore aligned after a refresh.

You can simply use the "Realign" button in the control panel of the given elements.
Beware, it will realign the text even if you customized their positions. This is why this realignment is not automatic.