You can identify that Span.FixColSize is obsolete and avoid using it when designing layouts in MDriven Designer.
Status
Span.FixColSize is no longer in use. It was related to Bootstrap-based layout behavior. Bootstrap is no longer available in MDriven, so this setting does not provide a supported layout mechanism.
Do not use this attribute when creating or maintaining a ViewModel. If an existing ViewModel contains it, treat it as a legacy setting and review the layout using the current layout behavior instead.
Current layout approach
Use the current Span and container layout settings rather than trying to control column size with Span.FixColSize. Span.CSSGrid is deprecated and defaults to true, reflecting the current layout direction.
For example, if a details area must use the available vertical space while a header and footer retain their natural size, configure the container layout so that the details area can grow. If multiple areas may grow, their growth values determine their relative share of available space; values of 2 and 4 allocate space proportionally, with the latter receiving twice the share of the former.
Related legacy attribute
Column.FixColSize has the same legacy Bootstrap relationship and is also no longer in use. Do not assume that changing one of these legacy attributes changes the current layout.