You can "zoom in" and out on your chart in TradeStation by using the up and down arrow keys. This changes the spacing between bars, but if automatic sizing is enabled, you'll see the bars get larger in many cases as fewer bars are shown on the chart.
If you're trying to adjust the bar width in TradeStation and it seems to have no effect, it may be due to your Chart Analysis Preferences settings. For example, if you're trying to thicken the MQ Trender Pro 2.0 plots, the bars may still not reflect the increased weight you've selected for each of its plots.
When you enable the Auto-size bar and drawing object weight when bar spacing changes option, manually adjusting the weight has no effect. Try disabling this option by unchecking the box to see if weight adjustments start working again. This option is highlighted in red in the image, below.
Note that in TS 9, Chart Analysis Preferences is available under the View menu, and is only available when you have a chart selected.