Sets a new @value for an existing meta data item or adds a new item. Meta data @tag names can be something like e.g. "comment". Supplying %NULL for the @value will unset an existing value.
preset name
meta data item name
new value
Return: %TRUE for success, %FALSE if e.g. there is no preset with that @name
See Implementation
Sets a new @value for an existing meta data item or adds a new item. Meta data @tag names can be something like e.g. "comment". Supplying %NULL for the @value will unset an existing value.