The primary reason why Zoom limits the number of displayed participants to 25 concurrently displayed in the gallery view is due to the additional computational power required to handle a greater number of thumbnails.

As such, the ability to extend this default amount to 49 is dependent upon the processing power of your computer.

Zoom publishes the following guidance for the current processing requirements for enabling 49 participants.

If your computer does not meet the above specifications, then the option to increase the number of participants in the gallery view to 49 below will likely not be available.

If your computer is capable of handling the higher number of participants, the ability to do so will be available from the video settings tab within Zoom settings.