Should the dashboard left navigation be collapsible or should it remain expanded at all times? What are the pros & cons? In addition to this, how does it affect conversion rate?
Always keep in mind that an application can be used thousands of users on hundreds of screen sizes, screen resolutions and browsers.
Therefore, even though side navigation menu in a Dashboard application is highly important, the users SHOULD be able to collapse it. Maybe not all the way, refer the screenshot below.
It definitely depends firstly on the content itself (content on the right side). Let's consider why a user needs to collapse the left navigation;
- The content is crowded and user wants to focus only on content,
- The screen size is small and user needs space.
In fact, both of the reasons are related to "space". If your users need space, then you should give it to them. If not, then firstly try without collapsing feature and gather feedback from your users.
Collapsing feature is sometimes complex as some navigation patterns are nested and need attention to create a usable interaction, so why to make effort when your users do not need it?
So, it's better to take action based on your user's need. Then go on taking new actions as user needs evolve over time.
Space is a very general opinion and we should not decide on expanding or collapsing based on space. The real decider in this situation is Content on the sidebar.
Questions to ask are:
How important is the content on the side bar? How frequently does the user use the options displayed on the sidebar?
High Frequency and important: You know that it should not be collapsed and always kept handy on screen.
Low Frequency but important: It can appear collapsed. A user will find his way to menu.
Low Frequency and additional option: Keep collapsed and if you ask me, I would not bother adding the option at all.
Let me know if this helps.