1. Color settings (swatches, scratch pad, and gradients) are stored in the sai.ssd file located in the installation directory. If it is renamed or removed, then SAI will generate blank copy in its place. This is useful if you want to back up your color sets or just want to create a new one. For the coordinates and size of the swatches, you can edit and then un-comment the respective lines in the misc.ini file, also found in the installation directory.
2. Go to the options menu and you'll see the path for temporary files (a.k.a. virtual memory dedicated to SAI). Normally it's blank by default, which is the same folder as the installation directory. Those temporary files are created by SAI to keep track of actions for undo and redo, and they are erased after SAI exits normally. If SAI crashes, then these files will remain behind which contain a portion of the unsaved data. These files may be deleted manually but it's generally a good idea to save them in case you want to recover anything useful.
3. When using blending and blur brushes, make sure to set the color on erase mode (transparent). If not, then a trace amount of foreground color will be added. This is by no means saying the extra color is bad, because in come circumstances you may use this feature to create a light tint while blending colors.
4. The "detection source" flags one of your layers (highlighted green) to become the "reference" for the paint bucket and magic wand. This makes the tools only "see" the flagged layer, and not others (when set to the detection source, of course). This can be very useful if you want to work with other layers visible but not wanting them getting in the way.
5. Double clicking on a tool opens up the custom tool settings. Here you can choose to override the stabilizer controls for that individual tool only. This way you can switch tools with different stabilizer preferences without having to switch the "global" stabilizer every time.
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