I recently released a series of three Mouse Grid-related applications (they are free and open source; see this board's "Third-Party Command Utilities..." forum). They are: "Screen Grid" which puts an user-configurable grid over the entire multi-monitor screen; "Monitor Grid <1-10>" which places a similar grid on just the selected monitor; and "Window Grid" which puts the grid on the currently-active window. Each application's grid can have up to 26 columns and 10 rows (all are independent, they did not share preferences); the user may adjust the font (family and size) of the grid cell labels; the user may adjust the size and color of the grid lines; the transparency of this grid is user-adjustable.

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-Edgar
DPI 15.3, 64-bit Windows 10 Pro, OpenOffice & Office 365, Norton Security, Shure X2U XLR to USB mic adapter with Audio Technica DB135 vocal mic, Asus X299-Deluxe Prime, Intel Core i9-7940X (14 core, 4.3 GHz overclocked to 4.9 GHz), G.SKILL TridentZ Series 64GB (4 x 16GB) DDR4 3333 (PC4 26600) F4-3333C16Q-64GTZ, NVIDIA GIGABYTE GeForce GTX 1060 GV-N1060G1 GAMING-6GD REV 2.0 6GB graphics card with 3 1920x1080 monitors