Graphical user interfaces called pplane and dfield for phase-plane analysis have been developed at Rice University, http://math.rice.edu/, and are available for academic use.

For MATLAB 2017a, use the following versions: pplane9.m and dfield9.m.
For MATLAB 2014b-2016b, use the following versions: pplane8.m and dfield8.m.
If you have a newer version of MATLAB you can instead use the Java version available on
https://www.cs.unm.edu/~joel/dfield/

Check out as well this MATLAB app for plotting phase portraits. It works with full functionality for R2020b version or newer.

https://se.mathworks.com/matlabcentral/fileexchange/81026-phase-portrait-plotter