Select Options > Continuous Drawing to draw continuously without having to restart the current drawing tool command. The line/arc/curve will keep drawing until you select another tool or hit the Esc key. 

Select Options > Continuous Drawing.

Select the desired drawing tool, i.e., Line Tool.

Click on the Editor to place the first point of the line.

Click to place the end point of the line.

Click to place the end point of the next line. The end point of one line will be the start point of the next line and will be connected to the previous line. 

Continue clicking points to drawing the lines of your design. 

To stop drawing, select another tool or command, or hit the Esc key.

Unselect Options > Continuous Drawing 

Select the desired drawing tool, i.e., Line Tool.

Click on the Editor to place the first point of the line.

Click to place the end point of the line.

The drawing tool will stop drawing after the current drawing command has been completed. If you want to draw another line, you will have to click on the editor to place the first point of the new line.

Unselect Options > Continuous Drawing.

Select the desired drawing tool, i.e., Line Tool.

Click on the Editor to place the first point of the line.

Click to place the end point of the line. 

After the current line is drawn, you will have to click to place the first point of the next line. 

The lines will not be automatically connected together.