It’s nearly impossible to build a complex application without the right tools and proper direction. Add the need to deliver products and iterations quickly, and application development grows even more challenging–if not unattainable. Also when working from home a need for visual workspace arises at a much more rate where multiple teams or individuals can come and collaborate.
Here is a list of tools that you can add to your inventory to work with ease:

Whimsical
Whimsical is free to use tools to work. It provides communicates visually at the speed of thought – collaborative flowcharts, wireframes, sticky notes, and mind maps. But, If you are using the free version of it, then you are only limited up to 4 whiteboards only.

However, 4 are very much sufficient for me as I don't work at a much larger scale. If you want more, you can upgrade as per your wish. One drawback is that currently, its mobile version is not available, if you want to access Whimsical the only way is through your desktop/laptop.

Miro
Miro is the online collaborative whiteboarding platform that enables distributed teams to work effectively together, from brainstorming with digital sticky notes to planning and managing agile workflows.

You can easily create mind-maps, user stories, flow charts, and many more.

LucidChart
LucidChart provides excellent features for the designer as for the creation of flowcharts, use case diagrams, flowcharts, and many more sort of documents at a very easy.

At a free version, you are, limited to only a few workspaces and in each workspace, you can not add more than 60 shapes. Although it works pretty much well for me under 60 shapes.

Creately
Creately is a web-based diagramming tool, that supports many diagrams types including Flowcharts, Venn diagrams, storyboards, etc, which are commonly used in teaching. Creately even has its own desktop software that automatically syncs with your online account, making it ideal for offline drawing as well.

Creately provides a very large variety of documents which is a very big advantage from all the above-mentioned tools.

Although all the above-metioned tools are very much attractive and using them once will always make you use again and again and going for the paid version is absolutely your choice as per your usage and love towards the tool.