You can create your own transitions, - see this tutorial for one method, The image below shows transitions I have created using this method. The procedure is the same in Movie Studio
Note: creating the icon image and preview video are extra steps to what is shown in the tutorial.they are located in the following folders, the name given to the icon image and preview videomust match the name you give the transition - I prefix mine with an underscore, as seen in the image above, to avoid conflict with exisiting Magix transitions:
Icon folder - use a jpg image 640 x 640pixels and put it in
C:\Users\Public\Documents\MAGIX\Common\Videocontent\Program name and edition\Plugins\GPU_Standard\Icons.
Preview video folder: create a WMV or MP4 video file, resolution 640 * 480 is big enough however do not go over 1920 x 1080, and put it in
C:\Users\Public\Documents\MAGIX\Common\Videocontent\Program name and edition\Plugins\GPU_Standard\Preview
Note: there is a bug in the preview of user created transitions - the playback is monochrome.
I'm not sure I fully understand your question, especially the reference to "slides" (or are you creating a video consisting of a series of still images rather than video files?) but yes, any and all transitions can be removed and/or to a limited extent (depending on which edition of MS you have) "edited".
First, this is best done in Timeline view rather than Storyboard view. When you place your slides, if you make sure there is NO gap between them AND they do not in any way overlap, there will be no transition. To remove such a transition, simply move the second slide until it exactly touches but does not overlap the edge of the first.
To edit a transition (I assume you have an edition of MS which includes a range of transition templates), if you insert one of those listed between the slides and then right-click on the transition icon you will see a drop-down menu with some options to allow "editing".
HTH, but if it does not, please post back with a more detailed explanation of what you currently do and what you would like to be able to do differently!
Such a lot of what can be done is hidden and accessible by right clicking within objects. I have made a habit of trying that with most of what I do and often amazed of what is possible.