Improve the selection and deselection of related diseases

[leicray]

Is your feature request related to a problem? Please describe.
LOVD3 allows curators to select the diseases associated with individual genes when editing a gene. The process involves selecting a disease from an enormously long list. If more than one disease is to be selected, this can be done using the Shift or Control keys, but it is prone to error if the user inadvertently releases the relevant key before the selection process is completed.

I think that it should be easier to navigate the list of diseases and the selection/deselection process needs to be made less prone to error.

Describe the solution you'd like
I would like to be able to navigate the list of diseases other than by scrolling through a long list. The selection/deselection process could be made more robust by use of check-boxes.