Controling the spacing (e.g. suppressing the space for multiplications)

I quote Joris’ message:

One may use the package ‘invisible-multiply’ to suppress the tiny space (for multiplications) altogether.

In ‘TeXmacs/packages/customize/spacing’, you may find several
other packages to control the spacing in math mode.

See here for a list of packages about controling the spacing.

To add a package, click Document -> Style -> Add package -> Add other packages..., input invisible-multiply (or other package names).