Hi Kristof! Thanks for reaching out and apologies for the delayed response. If you turn off "Enable Line Connections" in your View settings then you'll be able to place a line wherever you want on the shape. The only downfall is that it won't be physically connected with the shape so if you move the shape then the line won't move with it. 

Old post but if I am looking maybe others are.

This is how I do it:

1) Drag a new line shape onto the canvas.

2) Click and drag one end of that line shape towards your image.   

3) Continue to drag that endpoint into the image even though it will snap to a default point on the edge.  If you do this step slowly  the line connection point will re-join your mouse pointer and will connect to the image at the point you let go - the same way it does for most other lucid shapes.

Not sure when this became available as I see a few posts around still.   Note:  This doesn't seem to create a re-usable 'connection point' like Visio.  It just anchors to a xy or something on the image such that it survives moves and re-sizes.   If you want another line to 'use' the same connection point you have to drop your new line in the same place manually (as far as I can see).

Hope that helps!!

Hi there thanks for continuing this thread and posting about how you create line connections with images. This Help Center article also has more tips and tricks which can be useful when working with lines!

As you have mentioned it's not currently possible to reuse a 'connection point' for images in Lucidchart. However we're always looking for ways to improve and your feedback is the best way for us to do that. Would you mind adding your ideas to our feature request form? Ideas submitted to this form are passed on to the product development team for their consideration. 

Please feel free to let us know if you have any questions!