Problem:

When attempting to use the commands Join Linear Features or Remove Point From Linear Features, I receive an error in the heads up display: "Element not valid for this command".

Solution:

These commands are only valid for Point List Linear Features.  Check in the properties for the element to determine how this linear feature was created.  In this example, the linear feature was generated by linking codes:

In order to use the commands, you will need to convert the linear feature(s) to point list features.  This can be accomplished by selecting linear feature(s) using the MicroStation selection tool.  Hover over the element and select the command Convert to Point List Linear Feature in the context toolbar.